Flexible curtain rollup type doors are used in many industrial applications as barriers between the interior of a building and the exterior or between adjacent rooms in a building. It is desirable, depending on door location factors and use, to operate flexible curtain rollup type doors more or less manually, that is by actuating a door opening switch and a door closing switch, as well as by remote control. Moreover, there are instances when it is desirable to operate such doors automatically on a predetermined time schedule. Accordingly, such doors desirably include a relatively complex control system for controlling the door in various operating modes and for preventing operation of the door in the event of unwanted operating conditions.
Flexible curtain rollup type doors can benefit from the development of variable voltage--variable frequency alternating current (AC) drive motors and controls therefor, sometimes known as adjustable frequency drive (AFD) systems. Such motors and associated controllers provide for easy speed adjustment through changing frequency of the applied electrical energy. The use of this type of drive system for controlling a flexible curtain rollup type door provides for operating the door under positive control at all times, while also providing for rapid open and closing movement. Moreover, the use of variable frequency AC motor drives also provides for controlling the door to undergo so-called soft start and soft stop movement to thereby reduce stresses on the door structure and related components. Still further, it is desirable in the manufacture of flexible curtain rollup type doors to be able to provide a control system which will operate doors of various sizes and curtain thicknesses and weights. In this regard the need to maintain an inventory of various mutlispeed motors for driving the doors can be substantially reduced or eliminated.
There has also been a desire in the application of rollup type doors to be able to interface the door controls with other systems in large manufacturing and warehouse facilities, for example. Still further, there has been a desire to provide for the ability to interlock spaced apart doors in applications requiring a so-called airlock, for example.
There has also been a desire and need in the art of rollup type doors to reduce the door installation time and procedure, to provide suitable controls which prevent damage to the door during rollup and roll down movement and to provide for stopping the door in the event that the door curtain is inadvertently or accidentally displaced from its guide tracks due to, for example, excessive wind loads or the door being struck by a vehicle or person moving toward or through the doorway. In this regard also there is a desire and need to provide for controlling the operation of the door after the door has broken out of its guide tracks and during reinstallation of the door curtain and its bottom bar within the guide tracks. The needs and desiderata mentioned herein, as well as other needs and desiderata which will become apparent to those skilled in the art upon reading the following summary and detailed description, have been substantially met by the invention described herein.